// JavaScript Document

var current = 1;

function skip( eachBlock )
{
current += eachBlock;
if ( current < 1 ) current = 2;
if ( current > 2 ) current = 1;
visible( current );
}

function visible( oneBlock )
{
current = oneBlock;
for ( var dnum = 1; dnum <= 2; ++dnum )
{
var dv = document.getElementById("block"+dnum);
dv.style.display = ( dnum == oneBlock ? 'block' : 'none' );
}
}